2007A16 Briefly outline the components of parenteral nutrition, explaining the rationale
for the use of each component.



·   8.4MJ/day

·   Body can adapt to various macronutrient contributions


·   Daily requirement 2-2.5L/day

·   1.5L urine (minimum 0.6L)

·   0.4L resp tract

·   0.4L skin transepidermal diffusion

·   0.2L faeces


·   17kJ/g

·   Supplies 50% energy

·   Brain and RBC obligate (brain also ketones)


·   16kJ/g

·   Supplies 20% energy

·   20 essential amino acids required

·   Minimum ~0.5g/kg/day

·   Glutamine catabolized readily in fasting state


·   37kJ/g

·   30% energy requirement

·   e.g. linoleic acid


-Fat soluble

-Water soluble

·   A (e.g. eyes), D (bone density, Ca2+ homeostasis), E (e.g skin), K (coagulation)

·   B: many subtypes, e.g. B12 cofactor for methionine synthetase (DNA synthesis)

·   C: wound healing, skin health


·   Na+: nerve action potentials, ECF osmolality

·   K+: nerve action potential, ICF osmolality

·   Ca2+: muscle contraction

·   Mg2+: Enzyme cofactor e.g. Na+K+ATPase

·   Cl-: ECF osmolyte

·   PO43-: ICF for ATP synthesis and buffering


·   Fe2+: for Hb synthesis, cytochrome synthesis

·   Zn2+: cofactor in enzymatic reactions

·   I-: thyroid hormone synthesis

Special populations

·   Pregnancy: 1.2 x BMR, ↑↑protein requirement

·   Neonate: 2x BMR, ↑requirement of all

·   Elderly: BMR decreased

·   Sepsis: BMR increased, catabolic state, ↑protein requirement

·   Burns: catabolic state, ↑protein requirement

·   Large bone fracture: hypermetabolic and anabolic state, ↑BMR and protein requirement



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